For many Christians in the UK, what is currently happening in the USA is, at best, puzzling and, at worst, looks like a betrayal of Christian principles. And one question keeps raising its head: Whatever do Christians of the so-called 'evangelical religious right' think that they are doing in supporting Donald Trump?

To discover such Christian enthusiasm for a president whose words and actions are so often crude, stridently nationalist, anti-immigrant and, at time, misogynistic, seems at odds with the gospel, to put it mildly. In fact, the active involvement of Christians in the rise of US populism is so incomprehensible to many British Christians that it can feel like we are looking at activities on another planet. Now and then we hear a language that we understand...and then the person speaking it goes off and does something quite inexplicable. We are left asking: 'Why ever did they do that? I thought they were just like me!'

Clearly, the matter is complex but one of the biggest reasons is because US and UK Christians have drawn hugely different lessons from their common history. This became very obvious to me while writing a book (recently published) on 17th-century Christians, on both sides of the Atlantic, and their legacy. The book is titled When God Was King and, in short, it is about 'Puritans doing politics'. Writing this, it became obvious that many UK and US Christians are divided by a common history.

In the UK, the Puritans are a tainted brand. We might admire their dedication to reforming the church and their love of the Bible, but all that stuff about banning Christmas, plays, music, and sport on a Sunday afternoon all looks very joyless, judgmental and dull. Not to mention the slaughtering of Catholics in Ireland, which has left a legacy of bitterness that is still with us in 2018. And, anyway, all that 'Puritan politics stuff' fell apart when King Charles II was restored in 1660. After that, dissenting Nonconformists (the heirs of the Puritans) focused on rather less ambitious (but more positive) projects like social reform.

Not so on the other side of the pond. There the Puritan brand is still doing very well indeed. After all, it was Puritans (of one form or another) who set up their own version of an ideal community in New England in the 17th century (a 'New Jerusalem' in the 'New World') that has become such a key part of the cultural DNA of the USA. What's not to like about a turkey dinner at Thanksgiving, which was originally celebrated by Europeans and Native Americans sitting at the same table in 1621?

But the 'Puritan brand' has left more than just a taste for turkey and cranberry sauce in the modern USA. The settlers at Plymouth Colony (1620) and even more so at Massachusetts Bay (1630) thought that they were founding, as they put, it, 'a city on a hill'; a beacon of godliness, a Bible Commonwealth. It is not hard to see how this has morphed over four centuries into a belief in 'American exceptionalism'; even into strident US nationalism.

They set a precedent for a separation of church and state, but one in which the believers thought they had a big role to play in government. That, too, lies behind the quite phenomenal influence of a certain form of Christianity in the US political system, which actually has no national church and where church and politics are supposed to be separated.

Their legacy can also be seen in a very conservative and conformist form of Christianity and one that is confident about imposing this on others who don't subscribe to the programme. After all, it was a semi-theocracy that was (briefly) set up in Massachusetts Bay in the 17th century and one in which, in one town, 20 per cent of the adults in each decade found themselves charged with an offence, usually a morals violation. As the historian Michael Zuckerman has put it, they tried to create 'a totalitarianism of true believers'. And with women carrying names such as Be-Fruitful, Fear, Patience, Prudence, and Silence, it is not hard to see what lessons some men have drawn from that.

The first settlers generally got on fairly well with Native Americans but soon tensions rose and with it a sense that God had decided in favour of the European newcomers. Seeing vast numbers of Native Americans lost to European diseases, John Winthrop, in a letter written in 1634, concluded, 'God hath hereby cleared our title to this place.' Relating the destruction of a Pequot settlement (400 non-combatants killed) on the Mystic River, in 1637, Captain John Underhill wrote, 'sometimes the Scripture declareth women and children must perish with their parents... We had sufficient light from the word of God for our proceedings.' This did not bode well for future attitudes towards perceived 'outsiders'.

Finally, their strident millenarian focus on the imminent Second Coming still reverberates in the modern Protestant evangelical churches in the USA, even more than it does in the UK. It is a legacy that can be seen behind: climate change denial (God, not human agency, will decide the global future), opposition to gun control (be ready to oppose worldly government in an End Times conflict), Christian conspiracy theory (Antichrist is guiding the EU, the UN, the Catholic Church, etc) and the political agenda regarding the Middle East (where conflict may simply be seen as part of End Times events).

Now, the 17th Puritans are not really responsible for this. What we do with history is our decision and our responsibility. And, of course, we pick and choice in order to satisfy our own agendas. There was and is much to admire in the Puritan passion for scripture, personal holiness, social transformation, education and the importance of the individual.

However, it seems to me that some in the US churches have drawn on rather more controversial and contested aspects of the Puritan legacy. And these come with some health warnings: 'The 17th century attempt to dominate others did not work well then and it's not got better since'; and 'The gospel is designed for service, not for the control of others.'

We live in interesting days, Never think history has finished with us.

'When God was King: Rebels & Radicals of the Civil War & Mayflower Generation' by Martyn Whittock is published by Lion Hudson, price £9.99.