Sea Lion and Germany bombing UK are examples of strategies that can be hard countered by allied response. With Sea Lion, UK buys 6-8 infantry R1. With Germany bombing, russia buys land units and bullies Germany.
Sealion isn’t necessarily a bad move for Germany. The trick is to do it properly and leave yourself a way out (don’t commit 100% to it). If for example Russia doesn’t destroy a German fighter and Germany spends nothing G1, the threat of an all transport purchase G2 forces UK to buy land units for the capital UK1, otherwise with a maximum of 8 units purchased UK2, there won’t be enough to defend on G3. If UK responds properly by placing a few land units on their capital on UK1, Germany can call off Sealion and switch to purchasing nothing but land units and go after Russia strong. The only drawback for Germany is that a few land units will reach the front later, but the total IPC worth of land units at Russia’s doorstep on G4 remains the same. The cost for UK is to lose their capital if they didn’t respond with land purchases, or to have extra idle land units on their capital for many turns if they did. I’m not saying it’s always the best move to do this with Germany, but in the right circumstances, it can work even against a good opponent.