Well,this is really a reversion to the pre-1914 situation, except that there is no empire. Hence no Royal navy and no colonial army. And remember that if in 1940 Hitler could have landed a couple of divisions in England, the Wehrmacht would have made short work of British resistance. Thinking further of course, the same would have been true in 1588. The Tudors effectively disarmed the English nobility and, hence, the people. The Spanish Infantry would have made hash of the England bands.
The Tudors had pretty good reason for doing so, as the idiot English nobility had spent the previous 40 years doing their best to exterminate each other, which is fair enough. Unfortunately, in the process they killed a whole lot of non-nobles, who didn't deserve it.
The Spanish Infantry of the time were far and away the best soldiers in Europe. They beat everybody, when they could come to grips with them. The Dutch were only able to hang on because it's hard for the infantry to charge when it's waist-deep in mud.