This belief about supporting Israel in our current time comes from dispensationalism, which is Only about 200 years old. It became popular in the late 19th century in America. So you have to ask yourself do you believe that God hid this interpretation from his people for around 1,800 years? Because before then most Christian’s believed that these events happened during the Reign of Nero.
Many truths of God's word were lost or suppressed up until the Reformation. Restoration of a number of truths has been progressive. For example, Martin Luther did not practice baptism by immersion, but he did remove the restriction on marriage for priests.
Did God hide these truths or were they there in His word all the time? The nation of Israel did not cease to exist in Nero's time. The diaspora was foretold in God's word, the consequence of Israel's rebellion. What could be worse than rejecting the Messiah? It was not just while Jesus was here. Israel hounded and persecuted the church relentlessly. Rome destroyed Israel while God looked on, not helping at all. The Roman general Titus reportedly refused to accept a wreath of victory, as there is “no merit in vanquishing people forsaken by their own God.”
There are many prophecies that can only be fulfilled with a restored nation of Israel. I do not say that Jews are saved automatically, far from it. They still mostly reject the true Messiah and they pay a price. However, God's promise remains and the fulfillment began in 1948.
I'm English and I was born as the British empire began to crumble post WW2. Britain threw Israel to the wolves even before there was a restored nation. There is nothing great about Britain now. America has been transformed over the same period of time. Britain was destroyed by two world wars, America was greatly enriched. America has been a staunch supporter of Israel while Britain chose to pander to the Middle East instead. I do not believe that this is coincidental. America herself has been slowly turning her back on God since the 60's. The moral rot has well and truly set in. The consequences are obvious. If America deserts Israel, then that will be the end of America as a great power, just as Britain's greatness is merely a memory in history books. Even that memory is being torn down by those who insist on judging societies of the past by the hypocritical standards of today.
From a purely natural point of view, Israel is the only remotely democratic nation in the Middle East. On that basis alone she is worth supporting. She is the only nation in the region where Jews and Muslims live together in relative harmony. People seem to forget that 25% of Israel's population is Arab and most of those are Muslim.