His support for the IRA is explained by the fact that he was born in Britain? I would have thought that makes it harder to explain, given how rare such an attitude is in the UK. Much more so than in the US, which was the source of most of the IRA's financial support.
Support for facism is also very rare here. I would be surprised if you could make a convincing case that it is more common in the UK than in the US. I imagine there probably isn't much difference.
And in any case, he apparently
moved to the US as a 'young boy'. Which was probably before he formed most of his political opinions.