The US/UK special relationship is longstanding. Throughout the post-WW II era, both nations have been imperial partners, the US calling the shots, Britain saluting and obeying.
Trump wants the unachievable. He wants a new nuclear deal and not to go to war with Iran. He needs to make the grand gesture soon, like firing John Bolton, but it may not be enough.
It seems that the Americans and British carried out the seizure operation not for the purpose of enforcing EU sanctions against Syria per se, but rather to simply antagonize Iran. Iran will have little choice other than to walk away from the nuclear treaty.
The submersible incident – complete with the speculative plot line of a US-Russia firefight in the Arctic – did drown, at least for a while, the prime, current geopolitical incandescence: the US economic war on Iran.