That keeps us weak
Can it not make us all stronger?
An England alone...a Scotland alone....a Wales alone.
The UK isn't a trading bloc; it's a personal and political union since Scotland asked to join with England in 1801. Wales is different; it was conquered the old fashioned way centuries before, however respecting (usually) the Welsh way of doing things has meant it wasn't simply assimilated into being a region or couple of regions. It's remained a country and a proud one, as Poland should and has cause to be.
ou would never had become an Empire
We would, and were well on the way to becoming one long before 1801. Though the role of Scots in developing the empire (especially Malawi and settling NZ and Canada) was strong, in part due to lack of resources at home.
But does the EU want to become an empire now? The age of empires is long dead and rightly so. And would Poland want to be a part of someone's empire, whether it's called empire, sphere of influence, lebensraum, russky mir or backyard. I doubt it, and would prefer to see Poland be Poland, for all its faults and strengths.
I doubt an EU would be a match for Putler, not least because the two dominant economies in the EU either were or are sympathetic to appeasement. I opposed Brexit, however even before there was always the question about what the EU should be. A trading bloc of fully independent countries is what it is, however there are those who would wish it to develop in another direction, largely for less than altruistic reasons.
China is the main threat now; one to resist rather than sniff out short-term commercial opportunities in.