This is a fascinating discussion. In my opinion, it is clear if your are anti-Zionist, you are antisemitic. If you are opposed to actions and policies of the present Israeli government you are not automatically antisemitic. After the inquisition, the Khmelnytsky Pogroms, the Pogroms in Russia and Poland in the late 19th and early 20th Century, the Zionist movement began looking for a homeland for Jews. This was crystallized further after almost 70% of European Jews were murdered under the most inhumane circumstances in history during the Holocaust. There is nothing evil or nefarious in the desire of a group of people who have systematically persecuted for 100's of years to want to have their own place to live.
As for antisemitism in the United States, it has always been here. As Jews have assimilated this has receded into the darkness. But it never vanished. I experienced this most of my life. I was beaten repeatedly as a child for being Jewish. My kids on the other hand have not experienced this at all. It didn't go away, it just went underground. The failure to speak out forcefully against this kind of behavior when it arises is a danger to our society. The idea that the people who serenaded the press with chants of JEW-S-A at the trump rallies did this because the US government supports Israel is so ridiculous as to defy common sense. Antisemitism existed before Zionism and it will continue to exist as long as we tolerate it. The idea that Jews control the media or the levers of power in the government and act in coordinated manner to benefit Jews and Israel is just plain nuts and to hold these views not only do you have to a highly distorted view of reality you have to by definition be antisemitic.
That doesn't make all Jews good nor does it mean the Israeli government is a paragon of virtue. I prefer the words of Victor Frankl in his book Man's Search for Meaning:
From all this we may learn that there are two races of men in this world, but only these two — the “race” of the decent man and the “race” of the indecent man. Both are found everywhere; they penetrate into all groups of society. No group consists entirely of decent or indecent people.
Victor Frankl Man's Search for Meaning