I know what you're thinking, brothers and sisters across the pond. Who's this British guy, and what the heck is he doing poking around in our business? Worry about your own country, and we'll worry about ours. Right?

Well I don't write this lightly. I've held off doing so because part of me imagined that what we've seen unfolding in the Republican nomination race was either an elaborate satirical joke, or more probably a fast-burning sideshow which would soon be consigned to history as a comical footnote. But it's neither of these things; support for Donald Trump to become the Republican Presidential candidate is more widespread than I could have imagined. What's more, many of the people supporting him, are Christians.

There's biblical precedent for a man from overseas to write to the church in another country about the stuff that's going awry there; lots of it actually. So that's who I'm writing to. If you're live by a different moral code, then I guess I've got no right to challenge you on your politics based on my beliefs. But if you're a part of the family, this is for you, and I don't think you can just dismiss me as a foreigner. We're part of the same Kingdom, after all.

Here's the main thing that I want you to hear: you, American Christians, wield immense power. Between you, you've got the sheer weight of numbers to decide any national election; especially one within the Republican Party. Right now, it actually looks like Donald Trump could realistically be elected as your next President. And you've got the power to make that happen; or to stop it.

Donald Trump. A man whose own Christian faith has never previously demonstrated itself to be of central importance until it was an election issue; who couldn't even quote an actual Bible verse when he was asked for his favourite. A man who seems to be very angry, and very sure that he's the one guy who can restore the American dream, without really spelling out what that even means any more, or how he intends to do it. You almost certainly don't know his specific policy ideas beyond the fact that he'll "change" things (which is exactly how Obama got elected) and "get tough", which is a pretty ominous phrase. Maybe you've got caught up in the excitement around a candidate with enough celebrity appeal and financial backing to seriously challenge Hillary Clinton. But just stop for a moment, and remember who this man is. He's a 'top' businessman who's managed to lose a fortune; who'd have been several times richer if he'd just banked the money he inherited. A guy who said he'd probably date his daughter if she wasn't his daughter.

Maybe you know all this, and you still believe that he's the pragmatic best (or least worst) choice for America. Then let me say this: if you're truly a Christian, then while your earthly leaders are important, you first follow Jesus Christ. Your first allegiance is not to your nation, but to a man who said "greater love has no one than this, that he lay down his life for his friends"; who called you to life of submission and service when he said that "if anyone would be first, he must become the very last, and the servant to all." Jesus brought the politics of reconciliation, love, friendship and compassion, not anger and disharmony. He didn't promise to "get tough" on sin and the causes of sin. He allowed himself to be whipped and tortured, forgave those who did it to him, and gave up his life on a cross so that sin might be dealt with and you might know eternal life.

But of course, Jesus isn't running in this race. So as a Christian, it's your job to work out which of those candidates best aligns with who he is, and who he calls you to be. I am pretty confident that whatever the answer is, it isn't Donald Trump.

I'm not asking you to vote for Hillary Clinton, or even to vote Democrat. I'm also not insulting your intelligence; I'm not calling those who support Trump racist or stupid. I know that there are many complicated issues in your country which I don't properly understand; reasons for immense frustration among much of the electorate for which you blame the current President. You want "change"; you want a President who is going to fix the biggest presenting problems in your society. To repeat myself: I'm pretty confident that whatever the answer is, it isn't Donald Trump.

Genuinely, we the outsiders want to let you know how terrified we are about the eventual possibility of a President Trump. If that transition from scoffing Saturday Night Live gag to nightmarish reality actually occurs, then a whole lot of concerns are created, both in the US and beyond. What happens to the already simmering pot of racial and religious tension in America? What happens to the financial markets, which will almost certainly react with shock to such an election result? What happens to the poor? Christians, you're supposed to care about them, even above yourself.

Internationally, the picture is even scarier. There's a chance that the whole world will become more unstable than it already is. In the Middle East, governments and terrorist groups alike will only become more desperate, more alienated. The US relationship with superpowers Russia and China could become destabilised and quickly tumble into crisis. There will almost certainly be more wars. And do you really want to put the nuclear button into Donald Trump's hands? Because if he decides he needs to find the ultimate way to "get tough", then that only ends one way.

Perhaps you think I've gone too far. So let me pull it back. We're scared, America; really scared. You can tell that's true of us Brits when we keep making jokes about something. But we love you. We love your beautiful country; your countless kind, wise, brilliant people; your many wonderful exports. You're the nation of Reese's Peanut Butter Cups, of the Muppets, Tom Hanks, Deep Pan Pizza, Basketball and Bruce Springsteen. Please don't also be the nation of President Trump. God knows, you are so much better than that.

Martin Saunders is a Contributing Editor for Christian Today and the Deputy CEO of Youthscape. You can follow him on Twitter: @martinsaunders