Why is war the only way to cancel a tribute?

I'm playing as England and I've been planning a Denmark invasion for quite a while. I started sending over one full stack, then another, then another, and I'm still not sure I can pull it off. Denmark seems to be the most secure node in the whole game, they literally have more than 7,000 soldiers around their capital, and it has taken longer than I expected. I've been keeping my stacks within their city limits, having purchased military access for 1,000 a turn, although when I saw they have a lot of really advanced technology I decided to try and buy it. First, I don't understand how they had technology so far beyond every nation in the game, but anyway, after they said 50,000 wasn't enough for National Passports I decided to offer 30,000 a turn for 20 turns. I was planning on cancelling it the next turn but there is no way to cancel it without declaring war! If I declare war then I lose important alliances everytime...I was hoping to cancel the tribute as a way to provoke them into attacking me...but that function (cancelling tribute) seems removed....anyone know why? I'm going bankrupt now...

Denmark are the most annoying faction, ever! I had the same problems. I sent over three highly trained, elite armies - and they all perished. I wouldn't bother dealing with them. Lure them out of their capital from both north and south invasions, then strike them where it hurts with an invasion of Norway then military access to Sweden and knock down Copenhagen.

I managed to topple Copenhagen in 3 turns. First turn I attacked with my army of 4,500 against their army of 7,000 and I managed to slaughter their first army, along with whatever reserves were dumb enough to slowly trickle into the midst of chaos with my cavalry, striking their artillery and flanks. For some reason they suicided 2 generals right away, just riding into my battle line, which gave me a big moral boost and the first wave was rather easy. Eventually they got smart to the fact they were being slaughtered and once my cavalry died they they compiled a brand new army of 2,000 men. They didn't charge this time, which worked to my advantage, because the battle timer ran out and I was very low on ammunition. In all I killed about 2,200 and lost 1,000, so I thought I was doing well...I ran into trouble when 1 of my 3 armies retreated so far south they couldn't fight in the 2nd attack, but luckily I was able to pull it off and liberate Copenhagen. It's my first campaign on H/H and I didn't expect it to be so hard. I was seemingly rolling along but when I made the mistake of allying with Spain it all fell apart. It's really hard to fend of Prussia, Austria and France. The most ridiculous part is I lost my alliances for aligning with Spain and now Austria/Prussia and France are all teamed up with Spain! The hypocrisy!

Well I got back at Spain by sinking one of their fleets right after trading 15,000 a turn for 2 turns in exchange for a "peace treaty" and the Baltearic Islands.

Denmark is easy to beat. You send an army into the southern part of denmark and raid those farms. Their armies cross the land bridge/arrow thingy out of copenhagen to kill you. you put your fleet in between it blocking danish access back. You can then dispose with copenhagen at will.