This is possibly the nuttiest of the odd things Trump has said. But maybe he means no harm, just brash NYC talk.
Yes, between this and Cruz's "armor of God" comments, Iowa seems to bring out the nuttiness in GOP candidates as they try to one-up each other over who loves Jesus more in a state that has gone blue in 6 of the last 7 presidential elections.
Cuba was known as a Catholic nation. To me, Trump’s message makes sense. One would expect Catholics to come out of Cuba.
Sure he means harm by it. He's smart enough to know Cruz is pulling in heavy evangelical support, so he wants to create a wedge between Cruz and evangelicals, just as a number of pro-Trump folks here do all the time, making base and vile attacks on Cruz'a character a regular part of these discussions.
Those sorts of attacks don't work on politicians like Hillary, because her demographic doesn't really care how bad she is, morally, or what she believes theologically. But the Cruz evangelicals do care about such things, and Cruz's plan to substantially increase evangelical participation relies on him being able to establish and maintain trust with evangelicals.
So Trump or one of his advisors has probably identified there is a certain percentage of evangelical votes he could peel off if he made them worry Cruz was not an authentic evangelical, and what better way to do that but by innuendo that real evangelicals don't come from Catholic/communist countries. If so, the objective would be to sow suspicion, and weaken his appeal to as many evangelicals as possible.
My own belief is this is not a workable strategy for Trump. The number of evangelicals who would be put off by this would be more than offset by Trump-backing evangelicals who see this as slimy behavior and lose some confidence in Trump's own proclamations of evangelical values. Put another way, for Trump, this is a loser's strategy, and whoever advised him to use it should be fired. I'd pay good money to see that. "You're fired." :)
Peace,
SR