With all due respect to your pride, but the times are a changing. You know very well that contemporary Germany is not the country you have to fear. Beside of that it is not Poland to decide wheter Germany is a member of the European family or not.
The problem might be that Germany is a country you Poles export/import roundabout 30% to/from while Germany exports/imports roundabout 3% to/from Poland. The fact is, that Poland is completely dependent from the access to the German market. If you would not be allowed to do so, Poland will fall into the economical status of Belarus (the "North Korea" of Europe) while Germany is for sure not reliant on Poland or its markets (BuHuHaHa!). I also do not like the comparisons between our countries with the US/Mexican situation but economically they hit the point for sure. There are many nations of Europe who want to cooperate with us because they simply like us as their reliable partner. If you Poles do not want to do this is okay with me. You even can try to convince the rest of Europe. Just ask the EU-nations which partner is more important to them. Poland or Germany. You should start with your direct neighbour, the Czechs.
Nevertheless your President well advised to leave this summit and tell everbody that he want absolutely no connection to my country. He even can close the boarder. No problem. Germany will survive it for sure. If you search for friends in your neighbourhood you can turn to Russia then. Have fun with Puttie Pooth.
Well, Puttie Poot is not an option here, but there are other neighbors to have fun with - for instance Ukraine, Baltic states and Georgia. Potentially they could make up a strong alliance supported by the USA or even form their own Eastern European Union (EEU) within or outside the EU with uncertain results. The near future of Europe seems to be a damned interesting show!