The reactions to the Treaty by the other powers were far from swift. On one hand, communication was slow and untrustworthy, on the other hand the New World was much smaller (as mentioned in another answer).
England (still Catholic) suffered from the consequences of the Wars of the Roses (1455 - 1485) and had not yet the resources.
France was suffering from the Hundred Years' War and the war against Burgundy.
Aragon concentrated in the Mediterranean (Sicily, Naples) and Venice had eyes only for the Turk.
So, the reactions came later. For instance, the quote from Francis I is absolutely not contemporary as he was born in 1494. It's a very popular quote but a part that it seems to be a reaction to an ambassador of Charles V in 1520 or 1530, I couldn't find the source, even though I looked in the French National Library site and elsewhere.
Later reactions came from England with Cabot and France with Cartier but that's outside of the question.
Information on the countries , from:
Bennassar, Bartolomé. « Tordesillas: el primer reparto del mundo. » Política Exterior, nᵒ 25 (1992). http://www.politicaexterior.com/articulos/politica-exterior/tordesillas-el-primer-reparto-del-mundo/.