The fallout from the closure of three U.S. banks in the span of a week is making it near-impossible for analysts to determine a fair valuation for stocks, as volatility in the U.S. government bond market surges to its highest level in nearly 15 years, market strategists say. That is due in part to increasing uncertainty around how the Federal Reserve will react going forward as it attempts to balance a spate of risks to markets and the economy. If you can’t price bonds, you can’t price stocks At…