England shares greater cultural similarity and goals with the US than it does with the EU, to whom it is currently aligned.
This is particularly evident in the case of language, support of the US on foreign policy decisions (including allying with the US in wars) and economic similarity (such as a free market economy,without excessive regulation of employers over leave, working hours, paternity obligations etc).
Becoming an unincorporated territory of the United States in the same way as Puerto Rico would be beneficial to both the US and the UK.
For the United States this would extend its territory and influence right into Europe without significant downside insofar as people from the UK emigrating to the US, whilst at the same time creating a larger economic block than the EU.