I get the argument, but "country" spans many orders of magnitude in size. I mean, deliberately extreme example, but I'm fairly sure the smallest of the discount supermarket chains near me is more powerful than the country of Tuvalu:
https://en.wikipedia.org/wiki/Tuvalu
https://en.wikipedia.org/wiki/Norma_(supermarket)
Also, one party being stronger doesn't mean fighting them is worthwhile, e.g. Iceland threatening to withdraw from NATO to win the Cod Wars: https://en.wikipedia.org/wiki/Cod_Wars
And and, also why the People's Republic of China hasn't taken control of the Republic of China after all this time: https://en.wikipedia.org/wiki/Taiwan
Countries that small are outliers and aren't really the point. It's about the size of the company, not the size of the country. Being too powerful for the smallest country isn't that interesting. Being too powerful for the median country seems like a problem, much less for the UK, which is at the ~90th percentile by population and #6 in the world by GDP.